WirelessHART is the evolution of HART. It is designed for process automation and has focused on robustness and security. At the data-link layer WirelessHART utilizes 10ms time slots for communications. These time slots can be dedicated to individual devices or shared amongst a group. At the network level, WirelessHART supports graph routing, source routing and superframe routing. In case of graph routing, paths are stored by each device and are used for forwarding packets. In case of source routing, the packet contains the information about the nodes from source to destination. In the latter case, a specialized form of graph routing a device forwards a packet according to superframe ID embedded in the message. It also supports broadcast, unicast and multicast transmissions. In order to ensure reliable transfer of information, WirelessHART supports connection-oriented communication.

The key features of WirelessHART include: channel hopping, multi-hop mesh network and TDMA for radio channel access. Channel hopping (also known as frequency hopping) allows devices to choose different channels for communication to avoid jamming and prevent using poor link-quality. WirelessHART uses packet-by-packet frequency hopping which helps to avoid multi-path fading and interference. In order to increase reliability, redundant communication paths provide path diversity. In order to provide contest-free utilization of the radio channel, TDMA is used to arbitrate and coordinate communications between the devices in the field. The devices can be allocated fixed time slots for accessing the radio channel. The communication link between devices is made secure by using join keys, session keys and data-link network keys. The security in the data transfer is achieved through encryption, authentication and integrity check.

HART is the industry-standard protocol for communicating with intelligent field instruments. Engineers are familiar with the tools (hand-held and system-integrated) and HART maintains backward-compatibility as new features are added to the standard.

HART has the widest installed base of instruments in the world and therefore it would only make sense to build on the customers understanding and usage of an existing system with wireless HART. Adding Wireless capabilities to HART enables the continued use of existing tools (simply update the EDD, DTM or DOF) while adding features to provide security and reliability.

The benefits:

• Use existing tools for commissioning (for example, HART hand-held)

• Along with new wirelessHART instruments, we can add WirelessHART to existing instruments (via adapter) rather than replacing the instrument – Robustness at a reduced cost

• Reduces training costs – WirelessHART is an extension of HART

• Security is built in – you do not have to specify it

No.  Although WirelessHART uses the same frequency range, it has several features built-in to provide a more reliable and secure network:

• Channel hopping to avoid neighboring networks

• Channel assessment to check that a frequency channel is clear before it is used

• Mesh network to provide redundant wireless pathways

• Data is encrypted

• Data is authenticated to check it has not been altered on route

• New devices are authenticated before they are allowed to join the network

No. WirelessHART is simply a modified wired HART standard. WirelessHART uses all the HART commands plus some extra ones (for example, security) to support wireless networking:

• WirelessHART is HART. It is part of the new HART 7 specification.

• HART 5 instruments can be upgraded to WirelessHART simply by adding a WirelessHART Adapter.

• WirelessHART instruments are commissioned with traditional HART tools, for example, HART hand-held.

Very! Testing has proven that in a correctly installed WirelessHART network, data reliability (i.e. data reaches destination) is almost 99.999 %:

• Each device must have at least 3 neighbors

•  20 % of the devices must be connected directly to the gateway

Very! Security is built into WirelessHART, cannot be disabled and includes the following features:

• Data Encryption –128bit encryption as used in banking

• Different encryption key used at each hop along the network

• Authentication – data is checked to see if it has been altered on route

• Frequency channels are changed at each hop along the network (makes it difficult to find the data)

• New devices must be authenticated before they can send data

Not when installed correctly. WirelessHART has been designed to work alongside other wireless networks using the ISM band (Industrial Scientific Medical – the same as WiFi) and is able to do so while maintaining a high data reliability (99.999 %).

• Channel assessment – check if a channel is free before it is used.

• Short messages (<4 msec)

• Channel hopping

WirelessHART is designed for process monitoring & control and asset management and as such can be applied throughout a process plant. However, the following applications benefit most from WirelessHART:

• Difficult or expensive to wire routes (tunneling under roadways – remote parts of the plant)

• Rotating equipment (kilns - water treatment) where slip rings are currently used

• Remote part of plant (tank farms)

• Short term measurement to help solve process problems

• Existing assets where plant availability can be improved by monitoring maintenance conditions with a plug-in wireless adapter

The majority of installed HART instruments (90%) do not have remote access to read process data and maintenance conditions. The use of a WirelessHART plug-in adapter is a low cost and low risk method of providing remote access.

• Process monitoring – Multivariable devices such as flow and temperature have other valuable process data to report

• Asset management and maintenance condition checking

– Read back the HART PV and compare it to the 4 to 20 mA value. Discrepancies would indicate calibration testing is required

– Read back valve position and compare it to the setpoint. An offset would indicate a mechanical problem

– Read back instrument diagnostics and enable remote trouble shooting

– Modify instrument configuration remotely

– Manage instrument database

The primary advantages of a wireless installation are cost savings in installation costs (Engineering, materials and installation) and installation time. Savings of 30% over wired installations are very common. The installation time in addition can be reduced by 75% (ABB delivered what would take 4-6 weeks to install in 4 days on an offshore platform)

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Little additional training is required for getting started. WirelessHART is HART so existing tools and software are utilized. The main learning is when a network of devices are used. Challenge 1) getting the variables into the control system: ABB has a seamless integration into 800xA developed and 2) Setting up a network of devices to perform optimally: ABB is not new to this and we have experts who have deployed wide networks.

Some tools must be upgraded to support EDDs for HART 7 devices and adapters, but your existing HART configuration software will continue to work. You must add the new EDD/DTM/DOF for your new WirelessHART instruments just as you would if they were new 4 to 20 mA instruments.

• Existing HART software will not require upgrading for your existing HART devices

• Add new EDD/DTM for you new devices